Lowell Green concludes his excellent analysis of Reformed interpretation of I Timothy 2:4:

The dire consequences of claiming human freedom in spiritual matters are staggering. Thereby, salvation is wrested from the hands of God and placed into uncertain human hands. To say that God would have all people to be saved, but that he is unable to bring this about, damages the doctrine of God. Luther held that God is all powerful and he does what he wants to do. God loves all people but he brings salvation to only some of them. Rather than trying to solve this mystery by human reason, one should assign what is unclear to the Deus absconditusand should focus upon God’s boundless love in Jesus Christ, Deus revelatus. The doctrine that salvation is totally in the hands of God is the deepest comfort for struggling sinners.